【摘要】 声波在气体中传播时,气体的热粘性效应会使声波产生一定程度的衰减,且气体的声吸收系数随温度的升高而增大。由于发动机的排气温度较高,热粘性效应引起的排气管道中的噪声衰减应加以考虑。基于准平面波理论,首次计算了考虑热粘性效应时不同温度、流速和管道尺寸下排气管道中的传递损失,分析了各参数对管道中噪声衰减的影响。结果表明,随着温度和频率的升高热粘性声衰减增强,而气流流速和管道直径的增加会降低直管中的热粘性声衰减。对于简单膨胀腔,传递损失的预测结果表明,热粘性效应使通过频率处的声衰减有所改善。更多还原

【Abstract】 The thermo-viscosity of gas can attenuate the sound waves in the propa- gation,and the sound absorption coefficient is increased with temperature.In view of the higher temperature of the engine exhaust gas,the effect of thermo-viscosity on noise attenuation in an exhaust pipe needs to be considered.Based on the pseudo-plane-wave theory,transmission losses (TL) of exhaust pipes are calculated for the first time for different temperatures,flow velocities and pipe dimensions.The results show that in- creasing the temperature and frequency can enhance the sound attenuation of a straight pipe caused by the visco-thermal effect,while the increase in the flow velocity and pipe diameter will reduce the sound attenuation.Prediction of TL of a simple expansion chamber demonstrates that the effect of thermo-viscosity improves the sound attenua- tion somewhat at the pass frequencies.更多还原